ONE of the best things about Las Vegas, one of the few truly 24-hour cities around, is that it can be whatever you want it to be, at just about any time of day.

Picture this: A shopping center, off-Strip, at 7 o’clock on a Saturday. In this shopping center, there’s a place called Nu Sanctuary Lounge. It’s not the sort of place you’d naturally gravitate toward on your first or second or third trip to Las Vegas, but it’s the kind of destination where locals like to hang out.

They can sit outside, order off the extensive hookah menu and people-watch. Because this isn’t just any shopping center. This is Town Square — a shopping, dining and nightlife complex designed to fool you into thinking you are actually in a real square, in a real town, in some fanciful place that manages to simultaneously evoke the South Florida of Addison Mizner and the Southern California of your Spanish Revival-Revival fantasies.

Except that you aren’t.

Never mind all that. That’s not what’s important. Inside the lounge, a 10-year-old boy and his mom are feasting their way through a 10-course tasting menu, just like we are a couple booths over. There are spaghetti and meatballs and chicken fingers at Nu for the bar (and child) crowd, but our young gourmand is instead enjoying a perfect bite-size croque monsieur amuse bouche, gorgeous scallops with pancetta-heavy cauliflower risotto, foie gras two ways and a ginger root beer float.

Executive chef Brian Howard (who previously cooked at the delightful bordello-themed Cathouse at Luxor featuring lingerie models behind one-way glass) brings out many dishes himself, explaining the apple soda that comes with the raw Australian hiramasa — and how the honeydew, sprinkled with chili pepper on a bed of dry ice, is supposed to be a palate cleanser before the lamb entree.

It sounds involved, but it’s not, really. You can spend as little as $30 and get a four-course tasting menu; what we had goes for just $50. The menu changes often. You can customize. Want 12 courses? 15 courses? Fine. Want to spend $100 per person and also get wine pairings? Super. Want to party? No problem — Nu turns into a crowded nightclub as the evening charges on; if you’re hungry around midnight, the kitchen is still open to serve $14 prime filet/short rib/brisket-blend burgers. That’s also when local DJs/live music — and bottle service that can be 80 percent cheaper than the Strip clubs (check Facebook for 2-for-1 deals on $200 bottles of vodka) — bring in a thousand-plus locals and a handful of in-the-know out-of-towners, some of whom have to be kicked out when things shut down at 5 in the morning. (The management of the shopping center prefers that the health nuts showing up for vegan breakfast at Whole Foods not have to mix or mingle with the all-night party people.)

It’s places like Nu that remind us just how easily Las Vegas breaks down the barrier between dining, entertainment and nightlife; the idea of early curfews and community-board drama are completely foreign here.

Then again, it’s easy to break down the barriers when they’re barely there to begin with. Las Vegas has never been about borders or limits; the only limits are the ones it chooses to impose upon itself. This is how you find yourself in a situation (no pun intended) like the one we found ourselves in a couple weeks ago. That was when the off-strip Palms resort drew crowds not only for Jersey Shore brat Pauly D, who was that evening in residence at the casino’s Rain nightclub, but also for Matador Records’ 21st anniversary, indie-rock extravaganza a few steps over at Pearl, the flagship on-site music venue.

Check this: It’s 2 a.m. and Superchunk (killer set), Spoon and Belle & Sebastian have finished, but the party is just beginning. There’s free beer in the Palms ballroom, where other bands are playing. And over in the Palms lounge, there’s a Karaoke Underground event indie enough to make Silver Lake and Williamsburg hipsters weep with envy as they scroll through their Twitter updates. We notice a guy from our Park Slope subway rides a few years back — a member of the Upright Citizens Brigade — in the crowd. A crowd that, at one point over the weekend, also included Rob Corddry and David Cross at the Palms.

During karaoke, Ted Leo covers Beat Happening, surfs the crowd and then joins a group on stage covering Pavement’s “Summer Babe.” (Pavement didn’t play this song when it headlined the festival one night earlier but still dazzled the crowd with a messy, gorgeous set, full of We Really Hate Each Other conflict, in what might just have been its final show in the country.) Yes, the Vegas resort most associated with MTV has turned into CMJ after dark.

And this is one night after alt-rock legends Weezer played the Mirage’s Bare pool club, a place that’s known for bikini-optional partying; that evening, it also became a great music venue. The Light Group, the Vegas nightlife/hospitality pioneers who operate Bare, are pros at venues that do double duty. Nightclubs under its management, such as the consistently buzzing Haze at Aria, often host high-profile performances, while its sceney celeb-laden restaurants like Fix at Bellagio and Stack at the Mirage offer sizzling lounge scenes on those nights when you want nightlife but not a nightclub.

Dining also meets nightlife over at Steve Wynn’s Encore. There’s Botero (a fave of Paris Hilton before Steve Wynn banned her from his resorts after her recent drug arrest), where beautiful people gorge on steaks before heading to the adjacent XS, still the finest nightclub in Vegas even after the departure of partners Victor Drai and Cy Waits. And the Switch restaurant (good steak here too, making the fact that new vegan Steve Wynn has mandated vegan dishes at all his restaurants amusing) is part of that whole Encore Beach Club/Surrender nightclub colossus.

And for even more refined dining-meets-nightlife, there’s Sage at Aria, the best restaurant at CityCenter, which features fantastic farm-to-table American food and a happening bar with a cocktail list that holds up against any mixologist-driven spot in the city. Yes, this is fine dining, but then you see the absinthe cart being pushed around and realize that it can be something entirely different, too. If you want.